In-situ solidification remediation method and system for river and lake sediment

Abstract

This invention relates to the field of ecological restoration technology and discloses an in-situ solidification and remediation method and system for river and lake bottom sediments. The method includes: using sensing components to collect mechanical vibration signals of a coaxial dual-channel jet gun and back pressure signals of pipeline fluid; calculating the equivalent acoustic impedance index and normalized flow resistance deviation of the contact medium; mapping the medium into a hard or soft category based on the above characteristics; when determined to be a hard category, executing a penetration enhancement mode, outputting a high-pressure jet and injecting a low-viscosity remediation material; when determined to be a soft category, executing a viscosity lockout mode, outputting a low-pressure fluid and injecting a high-viscosity remediation material; simultaneously monitoring the turbidity diffusion flux index during the operation, and executing a negative pressure reverse suction operation when the melting condition is triggered. This invention automatically switches the operating mode through multi-physics field signal feedback, which can take into account both the breaking of the compacted layer and the in-situ coating of silt, adapt to different bottom sediment medium characteristics, and prevent secondary pollution.

Description

Technical Field

[0001] This invention relates to the field of ecological restoration technology, specifically to an in-situ solidification and remediation method and system for river and lake bottom sediments. Background Technology

[0002] River and lake sediment remediation is a crucial aspect of aquatic ecological restoration, with in-situ solidification technology being widely used due to its ability to fix heavy metals and organic pollutants in sediments through physicochemical processes. However, the actual underwater sedimentary environment exhibits spatial heterogeneity, with high-mechanical-strength compacted layers and high-water-content fluid silt interspersed within the same work area.

[0003] Existing in-situ sediment remediation equipment mostly employs preset, fixed operating parameters, maintaining constant grouting pressure, jet flow rate, and stirring speed throughout the entire operation. This singular operating mode is ill-suited to the complex geological conditions of underwater sediments. When the equipment encounters hard, compacted layers or sandy layers, the preset conventional dynamic parameters are insufficient to break down the sediment skeleton, preventing the remediation material from penetrating deeper areas, resulting in insufficient solidification depth or uneven agent distribution. Conversely, when the equipment enters areas of soft silt or floating mud, maintaining the high jet pressure used for breaking up hard soil can easily generate strong hydraulic disturbances underwater, causing a large number of sediment particles to become suspended and diffuse into the overlying water, leading to secondary pollution of the water body.

[0004] Furthermore, existing technologies can only inject repair materials with a single rheological property in terms of material delivery. While low-viscosity slurries have good permeability, they are easily lost with pore water in soft, high-water-content silt, making it difficult to form a stable consolidation framework. Conversely, while high-viscosity slurries have strong erosion resistance, they struggle to penetrate the micro-cracks in hard sediment. Simultaneously, conventional operating procedures lack proactive intervention mechanisms for construction disturbances. When an abnormal increase in turbidity is detected in the water surrounding the work site, only passive measures such as suspending operations can be taken. There is no immediate ability to recover and control the already formed localized high concentrations of suspended pollutants around the nozzle, leaving the risk of pollutants spreading with the water flow. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an in-situ solidification and remediation method and system for river and lake bottom sediments. This solves the problems that existing fixed-parameter operation modes cannot adapt to the highly heterogeneous underwater sedimentary environment, resulting in insufficient penetration and solidification of hard crusted layers, excessive hydraulic disturbance of soft silt layers, and reagent loss.

[0006] The first aspect of this invention provides an in-situ solidification and remediation method for river and lake bottom sediments, the method comprising the following steps: The coaxial dual-channel jet gun is placed in the working position, and the mechanical vibration signal of the coaxial dual-channel jet gun and the back pressure signal of the pipeline fluid are collected synchronously using the sensing components. The mechanical vibration signal and the back pressure signal of the pipeline fluid are processed by the central control unit, and the equivalent acoustic impedance index and normalized flow resistance deviation of the contact medium are calculated respectively. Based on the equivalent acoustic impedance index and normalized flow resistance deviation, the contact medium is mapped to either a hard medium or a soft medium.

[0007] When the contact medium is determined to be a hard medium, the in-situ solidification and remediation system is controlled to operate in a penetration-enhanced mode, outputting a high-pressure jet and injecting a low-viscosity remediation material. When the contact medium is determined to be a soft medium, the system is controlled to operate in a viscosity-locking mode, outputting a low-pressure fluid and injecting a high-viscosity remediation material. During the execution of the corresponding operation mode, the turbidity diffusion flux index of the operation area is monitored simultaneously. When the turbidity diffusion flux index triggers the set fuse condition, the current operation mode is interrupted and a negative pressure reverse suction operation is performed. The fuse mentioned here refers to the logical protection state of the in-situ solidification and remediation system forcibly interrupting the current operation process, rather than the physical circuit fuse.

[0008] In the above method, the step of calculating the equivalent acoustic impedance index using the central control unit specifically includes: performing a frequency domain transformation on the mechanical vibration signal to obtain the power spectral density function; and integrating the power spectral density function within a set frequency band using a frequency weighting function to obtain the equivalent acoustic impedance index. Specifically, the frequency weighting function is configured as a linearly increasing function or an exponentially increasing function whose weights increase with frequency, used to extract the high-frequency response characteristics of the hard layer.

[0009] In the above method, the steps of using the central control unit to calculate the normalized flow resistance deviation specifically include: performing sliding window averaging on the pipeline fluid back pressure signal to obtain the steady-state pressure value; calculating the incremental ratio of the steady-state pressure value relative to the stored pure water back pressure reference value to obtain the normalized flow resistance deviation; monitoring the rate of change of the normalized flow resistance deviation in adjacent control cycles, and maintaining the numerical output of the previous moment when the rate of change exceeds the set rate of change threshold.

[0010] In the above method, the mapping logic for the contact medium category is as follows: a two-dimensional feature space is constructed with normalized flow resistance deviation and equivalent acoustic impedance index as coordinate axes, and the decision region is divided in the two-dimensional feature space using a set acoustic impedance threshold and a set flow resistance deviation threshold; when the equivalent acoustic impedance index is greater than the set acoustic impedance threshold, it is determined to be a hard medium category; when the equivalent acoustic impedance index is not greater than the set acoustic impedance threshold and the normalized flow resistance deviation is greater than the set flow resistance deviation threshold, it is determined to be a soft medium category.

[0011] The specific execution steps of the infiltration enhancement operation mode include: controlling the high-pressure water pump group to output a high-pressure jet with a set pulse frequency, using the hydraulic wedge effect to break the bottom mud crust; controlling the fluid switching valve assembly to switch the passage, introducing the low-viscosity repair material exhibiting Newtonian fluid characteristics into the outer channel of the coaxial dual-channel jet gun; using the entrainment negative pressure generated at the jet nozzle by the high-pressure jet to entrain the low-viscosity repair material and inject it into the bottom mud fissures.

[0012] The specific execution steps of the viscous lockout operation mode include: controlling the high-pressure water pump group to reduce the output power and maintain a constant flow rate, outputting a low-pressure fluid in a laminar state; controlling the fluid switching valve assembly to switch the passage, introducing the high-viscosity repair material exhibiting non-Newtonian fluid characteristics into the outer channel of the coaxial dual-channel jet gun; using the low-speed rotation of the coaxial dual-channel jet gun to generate a shear force field, causing the high-viscosity repair material to undergo thixotropic liquefaction and mix with the bottom mud, and restoring the viscosity of the high-viscosity repair material after it leaves the shear force field to form a coating structure.

[0013] The turbidity diffusion flux index is calculated as follows: the difference between the real-time turbidity value and the set environmental background turbidity value is obtained using a turbidity flux monitoring array, and the difference is weighted to obtain the absolute pollution component; the rate of change of the real-time turbidity value over time is obtained, and the rate of change is weighted to obtain the pollution growth component; the absolute pollution component and the pollution growth component are summed to obtain the turbidity diffusion flux index.

[0014] When the turbidity diffusion flux index triggers the set melting condition, the negative pressure reverse suction operation includes: cutting off the supply path of the high-pressure water pump set and repair materials; isolating the high-pressure water pump set and connecting it to the vacuum negative pressure pump station; using the vacuum negative pressure pump station to construct a suction field through the inner channel of the coaxial dual-channel jet gun to recover suspended matter in the jet nozzle area; and determining the reverse suction duration based on the turbidity diffusion flux index when the set melting condition is triggered.

[0015] A second aspect of this invention provides an in-situ solidification and remediation system for river and lake bottom sediments, used to implement an in-situ solidification and remediation method for river and lake bottom sediments, comprising: The underwater operation unit includes a coaxial dual-channel jet gun for outputting fluid and repair materials, and the coaxial dual-channel jet gun is equipped with sensing components and a fluid switching valve assembly. The above-water feeding unit includes a high-pressure water pump unit for providing power, a dual-path rheological feeding unit for providing repair materials of different viscosities, and a vacuum negative pressure pump station for providing suction. The peripheral monitoring unit includes a turbidity flux monitoring array arranged around the perimeter of the operation area. A central control unit is communicatively connected to the underwater operation unit, the above-water feeding unit, and the peripheral monitoring unit, and is used to adjust the operation mode based on feedback from the sensing components and to execute fuse protection. The sensing components include a piezoelectric vibration sensor rigidly coupled to the outer wall of the coaxial dual-channel jet gun for acquiring mechanical vibration signals; and a precision pressure transmitter installed on the feeding pipeline for acquiring pipeline fluid back pressure signals.

[0016] This invention provides an in-situ solidification and remediation method and system for river and lake bottom sediments. It has the following beneficial effects: 1. This invention achieves precise quantitative identification of the physical properties of sediment media by collecting mechanical vibration and pipeline back pressure signals from a coaxial dual-channel jet gun and calculating the equivalent acoustic impedance index and normalized flow resistance deviation. The in-situ sediment solidification and remediation system automatically switches its operating logic between hard and soft media based on the identification results: for hard layers, it uses high-pressure pulsed jets combined with low-viscosity materials for deep penetration and fragmentation; for soft layers, it switches to low-pressure laminar flow combined with high-viscosity materials for in-situ coating. This adaptive mechanism solves the problem of poor adaptability of single operating parameters in complex riverbed geology, ensuring both the fragmentation of dense, compacted layers and the injection of reagents, while avoiding excessive disturbance and reagent loss caused by high-pressure jet impact on soft mud.

[0017] 2. This invention utilizes the coordination of a coaxial dual-channel jet gun and a fluid switching valve assembly to establish a synergistic response relationship between fluid rheological properties and hydraulic work. When treating soft sediment, the system uses the shear force field generated by the rotation of the jet gun to induce thixotropic liquefaction of the high-viscosity repair material with non-Newtonian fluid properties, thereby achieving thorough mixing with the sediment under low disturbance. When the mixture leaves the shear field, the material rapidly returns to a high-viscosity state, forming a locked skeleton. This solves the technical defect of easy failure due to gravity settling or water erosion in soft silt, thereby improving the structural strength and material retention rate of in-situ solidification.

[0018] 3. This invention establishes a dynamic environmental circuit breaker protection mechanism by monitoring the turbidity diffusion flux index, enabling real-time assessment of the diffusion trend of suspended matter during operation. When the turbidity diffusion flux triggers the set circuit breaker conditions, the high-pressure pump unit can be immediately shut down and switched to a vacuum negative pressure pump station. The inner channel of the coaxial jet gun is used to create a suction field in the nozzle area, allowing for immediate back-suction and recovery of locally high-concentration suspended matter. Attached Figure Description

[0019] Figure 1 This is the overall architecture of the in-situ solidification and remediation system for sediment of the present invention; Figure 2 This is the overall timing logic flowchart of the present invention; Figure 3 This is a graph showing the pollutant removal rate monitoring data of the water purification effect in an embodiment of the present invention.

[0020] The system includes: 10. In-situ sediment solidification and remediation system; 100. Underwater operation unit; 110. Coaxial dual-channel jet gun; 111. Inner channel; 112. Outer channel; 113. Jet nozzle; 121. Piezoelectric vibration sensor; 130. Fluid switching valve assembly; 131. Three-way solenoid switching valve; 200. Above-water feeding unit; 210. High-pressure water pump set; 211. Precision pressure transmitter; 220. Dual-path rheological feeding set; 221. Low viscosity feeding circuit; 222. High viscosity feeding circuit; 230. Vacuum negative pressure pump station; 300. Central control unit; 400. Peripheral monitoring unit; 410. Turbidity flux monitoring array. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] See attached document Figure 1 The present invention provides an in-situ solidification and remediation system for river and lake bottom sediments, including a bottom sediment in-situ solidification and remediation system 10. The bottom sediment in-situ solidification and remediation system 10 mainly includes an underwater operation unit 100, an above-water material supply unit 200, a central control unit 300, and an external monitoring unit 400.

[0023] The underwater operation unit 100 is used to physically disturb sediments and inject chemical agents at the bottom of the water body. The core component of the underwater operation unit 100 is a coaxial dual-channel jet gun 110 and its matching rotary drive assembly. The coaxial dual-channel jet gun 110 is connected to the upstream pipeline via a high-pressure rotary joint and is driven axially by a submersible motor mounted on the upper part of the gun body. The coaxial dual-channel jet gun 110 is made of rigid pressure-resistant material. Its internal structure includes a coaxially fitted inner channel 111 and an outer channel 112. The inner channel 111 is arranged along the central axis of the gun body, and its end connects to the central hole of the jet nozzle 113 for delivering high-pressure water jets. The outer channel 112 surrounds the inner channel 111, and its end connects to the annular gap of the jet nozzle 113 for delivering repair material slurry. The jet nozzle 113 adopts a recessed coaxial structure, in which the outlet plane of the inner channel 111 is recessed inward by a certain distance relative to the outlet plane of the outer channel 112, forming a premixing chamber. The recessed coaxial structure enables the high-speed fluid ejected from the central hole to generate negative pressure in the premixing chamber, thereby efficiently entraining the annular fluid flowing out from the annular slit.

[0024] A piezoelectric vibration sensor 121 is mounted on the shaft of the coaxial dual-channel jet gun 110. The piezoelectric vibration sensor 121 is rigidly coupled to the outer wall of the coaxial dual-channel jet gun 110 by means of threads or welding, and is located close to the jet nozzle 113 but avoiding the direct impact zone. The piezoelectric vibration sensor 121 is used to collect the mechanical vibration signals generated by the gun body when in contact with different media. The piezoelectric vibration sensor 121 is externally equipped with a water-sealed housing, and the water-sealed housing is filled with insulating sealant to isolate water pressure and corrosion.

[0025] A fluid switching valve assembly 130 is integrated at the proximal end of the coaxial dual-channel jet gun 110, immediately upstream of the jet nozzle 113. The fluid switching valve assembly 130 includes a three-way solenoid switching valve 131. The three-way solenoid switching valve 131 is housed within a pressure-resistant and waterproof chamber and connected to the surface control equipment via a watertight cable. The outlet of the three-way solenoid switching valve 131 is directly connected to the outer channel 112. The two inlets of the three-way solenoid switching valve 131 are each connected to the surface feeding unit 200 via independent pressure-resistant hoses. The arrangement of the fluid switching valve assembly 130 shortens the distance from the fluid switching point to the injection point, thereby reducing the time delay of fluid transmission in the pipeline.

[0026] A surface-mounted feeding unit 200 is arranged on a work vessel or floating platform to provide power and material sources. The surface-mounted feeding unit 200 includes a high-pressure water pump set 210, a dual-path rheological feeding set 220, and a vacuum negative pressure pump station 230. A precision pressure transmitter 211 is connected to the outlet end of the high-pressure water pump set 210, which is used to monitor the pumping back pressure in real time. The high-pressure water pump set 210 is connected to the inner channel 111 of the coaxial dual-channel jet gun 110 via a high-pressure pipeline. The suction port of the vacuum negative pressure pump station 230 is connected in parallel to the delivery pipeline between the high-pressure water pump set 210 and the coaxial dual-channel jet gun 110. A first electrically operated isolation valve is installed between the high-pressure water pump set 210 and the parallel connection point of the vacuum negative pressure pump station 230; a second electrically operated isolation valve, i.e., a vacuum isolation valve, is installed between the vacuum negative pressure pump station 230 and the parallel connection point. By cooperating with the valve group, high-pressure water is prevented from flowing back to the vacuum pump, and short circuit of the high-pressure pipeline is prevented during negative pressure suction. The vacuum negative pressure pump station 230 is used to provide reverse suction in emergency situations, and the delivery pipeline is connected to the inner channel 111.

[0027] The dual-path rheological feed assembly 220 includes a low-viscosity feed circuit 221 and a high-viscosity feed circuit 222. The low-viscosity feed circuit 221 includes a first storage tank and a first transfer pump. The first storage tank contains a low-viscosity repair filter media suspension exhibiting Newtonian fluid properties. The high-viscosity feed circuit 222 includes a second storage tank and a second transfer pump. The second storage tank contains a high-viscosity thixotropic gel with added thickeners, exhibiting non-Newtonian fluid properties. The low-viscosity feed circuit 221 and the high-viscosity feed circuit 222 are respectively connected to the two inlets of a three-way solenoid switching valve 131. Both the first and second transfer pumps are equipped with reflux lines to maintain the fluid circulation pressure within the lines.

[0028] The peripheral monitoring unit 400 includes a turbidity flux monitoring array 410. The turbidity flux monitoring array 410 consists of multiple turbidity sensors and flow velocity sensors distributed around the operating radius of the underwater operation unit 100. The turbidity flux monitoring array 410 is used to collect suspended solids concentration data and water flow velocity data at the operating boundary.

[0029] The central control unit 300 establishes electrical connections with the sensing components, the fluid switching valve assembly 130, the high-pressure water pump group 210, the dual-path rheological feed group 220, the vacuum negative pressure pump station 230, and the peripheral monitoring unit 400. The central control unit 300 integrates a signal processing circuit, which receives the analog signal from the piezoelectric vibration sensor 121 and performs analog-to-digital conversion and frequency domain transformation calculations. Based on the calculation results, the central control unit 300 outputs control commands to adjust the output power of the high-pressure water pump group 210 and the on / off state of the three-way solenoid switching valve 131.

[0030] See attached document Figure 2Based on the aforementioned in-situ sediment solidification and remediation system 10, this invention provides an in-situ solidification and remediation method for river and lake sediments: Initialization and preparation of the two-way loop: Before the operation begins, the dual-path rheological feed group 220 in the surface feed unit 200 is started. The first delivery pump is controlled to establish a full-flow circulation of the low-viscosity repair filter media suspension between the low-viscosity feed circuit 221 and the first storage tank. At the same time, the second delivery pump is controlled to establish a full-flow circulation of the high-viscosity thixotropic gel between the high-viscosity feed circuit 222 and the second storage tank. By establishing a full-flow circulation, the fluid is ensured to maintain the preset rheological state in the pipeline, and pressure fluctuations during pump start-up are eliminated. At this time, the three-way solenoid switching valve 131 in the underwater operation unit 100 is in the neutral closed position. The three-way solenoid switching valve 131 is a three-position three-way valve with neutral shut-off function.

[0031] Synchronous acquisition of multimodal signals and background calibration: The coaxial dual-channel jet gun 110 is lowered to a position close to the bottom of the water. The data acquisition module of the central control unit 300 is activated to simultaneously record the mechanical vibration signal output by the piezoelectric vibration sensor 121 and the fluid back pressure signal output by the precision pressure transmitter 211. In a pure water environment where the coaxial dual-channel jet gun 110 is not in contact with the bottom sediment, the average vibration amplitude over a period of time is recorded as a background noise reference, and the average fluid back pressure is recorded as a pure water back pressure reference. For the specific circuit implementation and filtering algorithm of signal acquisition, those skilled in the art can use conventional analog front-end circuits and digital filter designs, which are well-known technologies in the field and will not be elaborated upon here.

[0032] Joint solution of acoustic and liquid dual features: The central control unit 300 extracts features from the acquired real-time signals. For mechanical vibration signals, it performs a fast Fourier transform, converting the time-domain signal into a frequency-domain power spectral density function. Calculate the equivalent acoustic impedance index. The calculation formula is as follows: ;in: The set low-frequency cutoff frequency is used to filter out low-frequency flow noise and pumping ripple. To analyze the upper limit frequency of bandwidth; It is the power spectral density function; It is a frequency-weighted function; It is the frequency differential variable; To prevent numerical stability constants with a denominator of zero, a frequency weighting function is used to ensure the numerical stability of division operations in an absolutely static or extremely low background noise environment when the sediment in-situ solidification and remediation system 10 is in use. This is done to enhance the sensitivity of extracting high-frequency echo characteristics of the hard layer. It can be expressed as a linearly increasing function or an exponentially increasing function. Equivalent acoustic impedance index. It characterizes the ability of the contact medium to reflect and excite high-frequency vibration energy, used to distinguish between hard and soft media. It is also applied to fluid back pressure signals. Calculate the normalized flow resistance deviation The calculation formula is as follows: ;in: The average back pressure within the current time window; The pure water back pressure reference obtained in step S202. Normalized flow resistance deviation. It characterizes the rate of change of the rheological resistance of the medium at the nozzle outlet relative to pure water, and is used to distinguish between extremely soft plastic media and pure water media.

[0033] Medium state space mapping and mode determination: The central control unit 300 determines the equivalent acoustic impedance index based on the calculated value. and normalized flow resistance deviation The current state of the contact medium is mapped to one of three operating modes. The determination logic is as follows: if the equivalent acoustic impedance index... Greater than the preset acoustic impedance threshold The medium was determined to be hard sediment, and the in-situ sediment solidification and remediation system 10 entered the penetration enhancement operation mode. If the equivalent acoustic impedance index... Less than or equal to the preset acoustic impedance threshold And normalized flow resistance deviation Greater than the preset flow resistance deviation threshold If the medium is determined to be soft sediment or floating mud, the in-situ sediment solidification and repair system 10 enters the viscous locking operation mode. If the equivalent acoustic impedance index... Less than or equal to the acoustic impedance threshold And normalized flow resistance deviation Less than or equal to the flow resistance deviation threshold The medium was determined to be overlying water, and the bottom sediment in-situ solidification and remediation system 10 maintained standby exploration mode.

[0034] Adaptive rheology and hydraulic coordination: According to the locked operating mode, the central control unit 300 outputs control commands to coordinate the adjustment of the high-pressure water pump group 210 and the fluid switching valve assembly 130. When entering the permeation enhancement operating mode, the central control unit 300 controls the three-way solenoid switching valve 131 to connect the low-viscosity feed circuit 221, and simultaneously controls the high-pressure water pump group 210 to output a high-pressure breaking jet. At this time, the low-viscosity repair filter media suspension is entrained by the high-pressure water jet, and enters the microcracks of the hard sediment by utilizing the high permeability of the low-viscosity fluid. When entering the viscosity lock-in operating mode, the central control unit 300 controls the three-way solenoid switching valve 131 to connect the high-viscosity feed circuit 222, and simultaneously controls the high-pressure water pump group 210 to reduce its output power to a low-pressure disturbance state. At this time, the second delivery pump actively pumps the high-viscosity thixotropic gel to the outlet of the outer channel 112 of the jet nozzle 113, and merges it with the low-energy water flow from the inner channel 111 at the outlet. Due to the lower flow velocity, a strong entrainment effect is no longer generated; instead, a coating flow is formed, utilizing the thixotropic thickening properties of non-Newtonian fluids to create a local coating structure in soft sediment. Flow path switching is achieved through a three-way solenoid switching valve 131 at the near end, avoiding the pipeline replacement time required for fluid changes and enabling transient response to sudden changes in sediment properties.

[0035] Diffusion boundary monitoring and circuit breaker protection: The central control unit 300 continuously reads data from the peripheral monitoring unit 400. The central control unit 300 calculates the turbidity diffusion flux index. The specific calculation logic is detailed in the following description. If the turbidity diffusion flux index... Exceeding the preset circuit breaker threshold Regardless of the current operating mode, the central control unit 300 immediately triggers the hard fuse protection procedure: first, it forcibly shuts down the high-pressure water pump group 210 and cuts off the material supply passage of the three-way solenoid switching valve 131. After the precision pressure transmitter 211 detects that the pipeline pressure has been released to a safe range, the central control unit 300 controls the first electric isolation valve to close to isolate the high-pressure water pump group 210, then controls the second electric isolation valve to open and starts the vacuum negative pressure pump station 230. The sediment in-situ solidification and remediation system 10 uses the inner channel 111 to perform a negative pressure reverse suction operation, forming a negative pressure pool at the jet nozzle 113, cutting off the source of pollutant diffusion, and recovering high-concentration suspended matter in the near-field area of ​​the nozzle.

[0036] To ensure the continuity of the operation and the stability of the equipment, the central control unit 300 manages the operating state of the in-situ sediment solidification and remediation system 10 through built-in finite state machine logic. The state machine transition logic includes the following steps: Definition and initialization of the job state space: The central control unit 300 divides the operating status of the in-situ solidification and remediation system 10 into three mutually exclusive operating states, which are defined as: standby detection state. Enhanced penetration state and viscous locked state Standby detection state Corresponding to the operating conditions when the coaxial dual-channel jet gun 110 is in the overlying water or undergoing relocation operations, the goal of the in-situ sediment solidification and remediation system 10 is to maintain low energy consumption and monitor the environmental boundary in real time. (Enhanced permeability state) Corresponding to the condition where the coaxial dual-channel jet gun 110 contacts hard sediment or compacted layers, the goal of the in-situ sediment solidification and repair system 10 is to break up the hard shell using high-energy jets and to achieve deep penetration using low-viscosity fluids. (Viscous lock-in state) When the coaxial dual-channel jet gun 110 becomes trapped in soft sediment, fluidized mud, or high-water-content sediment, the goal of the sediment in-situ solidification and remediation system 10 is to suppress jet disturbance and utilize thixotropic gel for in-situ solidification and preservation. During the initial startup phase of the sediment in-situ solidification and remediation system 10, the central control unit 300 defaults to marking the current state as standby exploration mode. .

[0037] Real-time calculation of state transition criteria: The central control unit 300 in each control cycle Within, the equivalent acoustic impedance index calculated based on the aforementioned steps... and normalized flow resistance deviation Perform state transition determination. Define the state transition function. as follows: ;in: The target state for the next moment; The equivalent acoustic impedance index for the current period; The preset acoustic impedance threshold. The critical penetration resistance of the sediment is calibrated and is usually set to 80% of the measured acoustic impedance index of a standard sample of hard sediment under the same jetting conditions. This represents the normalized flow resistance deviation for the current cycle. The preset flow resistance deviation threshold is... The value is set according to the critical back pressure increment of the jet nozzle 113 in the fluid plastic medium, and is usually taken as 0.05 to 0.10. This is a state of enhanced penetration; It is in a viscous, locked state; In standby detection mode.

[0038] Based on the above criteria, the central control unit 300 maps continuously changing physical signals into discrete control logic, thereby realizing classified responses to complex underwater environments.

[0039] Anti-jitter and smoothing during state transitions: Considering the turbulence interference in the underwater environment and the signal fluctuations that may occur when the piezoelectric vibration sensor 121 comes into contact with the bottom sediment, the central control unit 300 introduces a time window anti-shaking mechanism to prevent the high-pressure water pump set 210 and the three-way solenoid switching valve 131 from frequently switching between different modes.

[0040] Set status confirmation time window Only when consecutive Calculation results within each control cycle Only when all indicators point to the same non-current state will the central control unit 300 confirm the status change and update the current status of the in-situ sediment solidification and remediation system 10. Status confirmation time window. It is usually set to 5 to 10 control cycles.

[0041] If the calculation result During the status confirmation time window An internal jump occurs, and the central control unit 300 maintains the state of the previous moment.

[0042] Hysteresis filtering logic ensures that the in-situ solidification and remediation system 10 only responds to stable changes in the properties of the sediment, avoiding malfunctions caused by instantaneous particle impact or bubble interference.

[0043] State-action mapping and execution instruction issuance: Once the current status of the in-situ sediment solidification and remediation system 10 is confirmed to be updated, the central control unit 300 immediately searches the preset action mapping table according to the new status attributes and issues corresponding control commands to the underlying actuators. When the status is updated to standby detection state... At this time, the central control unit 300 instructs the high-pressure water pump set 210 to maintain the minimum circulation pressure, which is set to 0.2MPa to 0.5MPa, and instructs the three-way solenoid switching valve 131 to close or switch to bypass circulation. When the status is updated to enhanced permeation state... At that time, the central control unit 300 instructs the high-pressure water pump group 210 to be upgraded to the high-pressure crushing mode. The pressure in the high-pressure crushing mode is set to 10MPa to 20MPa, and instructs the three-way solenoid switching valve 131 to connect the low-viscosity feeding circuit 221.

[0044] When the state is updated to sticky locked state At this time, the central control unit 300 instructs the high-pressure water pump set 210 to reduce to a low-pressure laminar flow mode. The pressure in the low-pressure laminar flow mode is set to 1MPa to 3MPa, and the three-way solenoid switching valve 131 is instructed to connect the high-viscosity feed circuit 222. The frequency conversion regulation of the high-pressure water pump set 210 and the electromagnetic drive of the three-way solenoid switching valve 131 can be implemented by those skilled in the art using standard PID control algorithms and PWM drive circuits, which are conventional techniques in this field and will not be elaborated upon here.

[0045] To accurately identify the physical hardness properties of the medium in contact with the coaxial dual-channel jet gun 110, the central control unit 300 employs a frequency domain feature extraction method based on power spectral density analysis. This method converts the time-domain vibration signal into a frequency domain index characterizing the acoustic impedance properties of the medium. The specific process includes the following steps: Preprocessing and windowing of time-domain signals: The central control unit 300 acquires the original analog voltage signal from the piezoelectric vibration sensor 121, and obtains a discrete time series signal after sampling by the analog-to-digital converter. To suppress spectral leakage and improve the accuracy of frequency domain analysis, the central control unit 300 performs time-series signal analysis. Apply Hanning windowing. Signals after windowing. Represented as: ;in: This is the sampling point index, with a value range of [value range missing]. arrive ; The length of the sampling window. The value is usually 1024 or 2048; This is the original sampled signal; This is the signal after windowing. Windowing smooths out the discontinuities at the edges of the truncated signal and reduces sidelobe interference.

[0046] Calculation of power spectral density: For the windowed signal A Fast Fourier Transform (FFT) is performed to transform the signal from the time domain to the frequency domain. Then, the one-sided power spectral density function of the signal is calculated. The calculation process is as follows: ; ;in: Frequency index; The result is the Discrete Fourier Transform. The imaginary unit; This is the summation index for the time-domain sampling points, with values ​​ranging from 0 to N-1; Sampling frequency Set the upper limit frequency to at least twice the analysis bandwidth of the sediment in-situ solidification and remediation system, typically set to 20kHz to 50kHz; Discrete frequency points The power spectral density value at that point. Power spectral density function. It describes the distribution of vibrational energy at different frequency components.

[0047] Band integral of the equivalent acoustic impedance index: Since rigid media tend to excite high-frequency vibration modes under jet impact, while soft media exhibit low-frequency damping characteristics, this embodiment uses the equivalent acoustic impedance index. To quantify the index, the integral formula in the continuous frequency domain is discretized into a summation form of frequency band energy: ;in: To correspond to the set cutoff frequency Frequency index, round ; This is a frequency index corresponding to the upper limit frequency of the analysis bandwidth of the sediment in-situ solidification and remediation system 10. ; These are the frequency weighting coefficients for discretization; To prevent tiny positive numbers with a denominator of zero, the value is usually taken as 10. Frequency weighting coefficients The design aims to amplify the weight of high-frequency components, employing a linear weighting method: ;in: For the frequency index currently being calculated; To correspond to the set cutoff frequency Frequency index, To correspond to the upper limit frequency of the analysis bandwidth of the sediment in-situ solidification and remediation system 10 Frequency index. By introducing frequency weighting coefficients. Equivalent acoustic impedance index It can provide high-contrast feature inputs for subsequent state determination. For the specific algorithm implementation of the Fast Fourier Transform, those skilled in the art can use the radix-2 FFT algorithm or utilize existing digital signal processing library functions; these are conventional techniques in the field and will not be elaborated upon here.

[0048] When the coaxial dual-channel jet gun 110 performs jetting operations, the periodic pressure pulsations generated by the high-pressure water pump unit 210 are superimposed on the actual medium flow resistance signal. To eliminate pumping noise and extract the back pressure drift caused solely by changes in the medium properties at the outlet of the jet nozzle 113, the central control unit 300 employs a normalized monitoring mechanism for flow resistance back pressure. This normalized monitoring mechanism transforms unstable absolute pressure values ​​into relatively stable dimensionless flow resistance characteristics through moving average filtering and ratio calculation. The specific processing steps include: Pressure signal buffering and noise reduction: The central control unit 300 continuously reads the current signal (typically a 4-20mA standard signal) transmitted by the precision pressure transmitter 211 via an analog input interface and converts the current signal into the corresponding pressure physical quantity value. Considering that the high-pressure water pump set 210 mainly adopts a plunger pump structure, the reciprocating motion of the plunger pump will introduce pressure ripples of a fixed frequency in the pipeline. In order to filter out high-frequency pressure ripples, the central control unit 300 establishes a length of... The first-in-first-out data buffer performs sliding window averaging on the collected raw pressure sequence.

[0049] Calculation of average back pressure within a time window: The central control unit 300 at each sampling time The average back pressure of the current time window is calculated based on the historical data stored in the buffer. The formula for calculating the moving average is as follows: ;in: The average back pressure within the current time window; The length of the sliding window. The typical value is the number of sampling points covering 2 to 3 complete mechanical operation cycles of the high-pressure water pump set 210, with a typical range of 50 to 200 sampling points, to ensure that the pressure ripple is effectively smoothed. Moving forward from the current moment The original pressure samples from each sampling point were averaged using a sliding window to obtain smoothed pressure values ​​that reflect the steady-state component of the current fluid transport resistance.

[0050] Solution of normalized flow resistance deviation: Due to variations in the depth of jetting operations and the length of the supply pipeline, absolute pressure values ​​lack universal applicability. The central control unit 300 incorporates a pure water back pressure benchmark obtained during the initialization phase of the in-situ sediment solidification and remediation system 10. For reference, calculate the normalized flow resistance deviation. The calculation formula is as follows: ;in: This represents the normalized flow resistance deviation. The average back pressure over the time window is calculated using the above moving average method. The pure water back pressure reference obtained in step S202.

[0051] Normalized flow resistance deviation It is a dimensionless value, normalized flow resistance deviation. This characterizes the incremental ratio of the degree of obstruction to the fluid by the external environment of the jet nozzle 113 relative to the pure water environment. When the coaxial dual-channel jet gun 110 is inserted into viscous soft sediment or fluidized media, jet diffusion is hindered, resulting in an increase in the average back pressure over the time window. Higher than the pure water back pressure benchmark This causes the normalized flow resistance deviation to be... The value is positive; when the in-situ sediment solidification and remediation system 10 is in pure water, the normalized flow resistance deviation is... Approaching zero.

[0052] Limiting and eliminating abnormal pressure fluctuations: In actual operation, pressure spikes may occur due to the instantaneous blockage of the jet nozzle 113 by large stones. To prevent transient interference from falsely triggering viscous lock-up, the central control unit 300 is equipped with a rate-of-change limiting logic. This logic calculates the rate of change of flow resistance deviation between two adjacent calculation cycles. : ;in: This represents the rate of change of flow resistance deviation. This represents the normalized flow resistance deviation at the current moment; This represents the normalized flow resistance deviation from the previous time step. If the rate of change of the flow resistance deviation... If the rate of change exceeds a preset threshold (typically set between 0.1 and 0.2), the central control unit 300 determines the current data as an invalid abrupt change and maintains the previous output value unchanged until the data returns to a reasonable range of change. This rate of change limiting logic ensures that the flow resistance monitoring mechanism only reflects continuous changes in the rheological properties of the sediment.

[0053] To achieve automated identification of the physical properties of sediment, the central control unit 300 constructs a two-dimensional orthogonal feature space based on acoustic and hydrodynamic characteristics. Within this two-dimensional orthogonal feature space, by defining decision boundaries, continuously changing sensor data is mapped to discrete media property categories. The specific process includes the following steps: Construction and spatial localization of two-dimensional feature vectors: The central control unit 300 will calculate the equivalent acoustic impedance index within the same control cycle. and normalized flow resistance deviation Combine to construct the current medium feature vector Medium feature vector Represented as: ;in: For medium feature vectors; This represents the normalized flow resistance deviation. The equivalent acoustic impedance index; This represents the vector transpose operation.

[0054] In a two-dimensional orthogonal characteristic space, the normalized flow resistance deviation is used. The horizontal axis represents the rheological properties and viscosity of the medium; the equivalent acoustic impedance index is used as the horizontal axis. The vertical axis represents the density and hardness of the medium. The central control unit 300 maps the sampling point at each moment to a coordinate point in a two-dimensional orthogonal feature space.

[0055] Delineation of decision-making boundaries and definition of regions: To differentiate between different operating conditions, the central control unit 300 sets horizontal and vertical straight lines as decision boundaries in a two-dimensional orthogonal feature space: the horizontal straight line corresponds to a preset acoustic impedance threshold. The vertical line corresponds to the preset flow resistance deviation threshold. The horizontal and vertical lines divide the two-dimensional orthogonal feature space into three decision regions.

[0056] The first region is a high-impedance hard region located on a horizontal straight line. = Above. The characteristic points falling into the high-impedance hard region indicate that the medium has high-frequency reflection characteristics, corresponding to the platen layer, sand layer or hard clay.

[0057] The second region is a low-impedance, high-viscosity region located on a horizontal straight line. = Below and located on a vertical line = The right side. Characteristic points falling into the low impedance and high viscosity region indicate that the medium has weak acoustic reflection but high flow resistance, corresponding to silt, fluid plastic clay or thixotropic sediments.

[0058] The third region is a low-impedance, low-current-resistance zone, located on a horizontal straight line. = Below and located on a vertical line = The left side. The characteristic point falling into the low impedance and low flow resistance region indicates that the medium has neither obvious acoustic reflection nor obvious flow resistance, corresponding to the overlying water body or extremely dilute floating mud.

[0059] Mathematical mapping of media attribute categories: Based on region division, the central control unit 300 uses a piecewise function to divide the medium feature vector. Mapped to a unique media property category The mapping logic is as follows: ;in: The type of media attribute to be output; This is a hard medium category, and the hard medium category corresponds to a permeation-enhanced state; This is a soft medium category, which corresponds to a viscous lock-in state. The water medium category corresponds to the standby detection status. The equivalent acoustic impedance index; This is the preset acoustic impedance threshold; This represents the normalized flow resistance deviation. This is a preset flow resistance deviation threshold. Through a two-dimensional spatial mapping mechanism, the central control unit 300 decouples the physical hardness and viscosity properties of the medium. When dealing with mixed sediments with high water content but containing gravel, the central control unit 300 will adjust its equivalent acoustic impedance index... Higher and prioritized for classification as hard media This allows for the activation of high-pressure jets for crushing, avoiding misjudgments caused by relying solely on pressure sensors.

[0060] When the central control unit 300 determines that the current medium is a hard medium, the central control unit 300 controls the in-situ solidification and remediation system 10 to enter the high-pressure wedging and low-viscosity seepage operation mode. The high-pressure wedging and low-viscosity seepage operation mode aims to solve the technical problems of difficult penetration into hard, compacted layers and difficulty in diffusion of the remediation agent in low-porosity media. The specific control strategy includes the following steps: Generation of high-frequency, high-voltage pulse jets: The central control unit 300 sends a high-speed crushing command to the high-pressure water pump unit 210 to increase the pumping pressure to the high-pressure reference value. High voltage reference value The pressure is typically set between 15 MPa and 20 MPa. To enhance the fatigue failure effect on the hard sediment skeleton, the fluid output by the high-pressure water pump unit 210 is not a constant flow, but rather a pulsed jet modulated to a set frequency. Jet pressure... The time function is: ;in: The jet pressure varies with time; This is the high-voltage reference value; For pulse modulation coefficients, pulse modulation coefficients The value is typically between 0.1 and 0.2; The pressure pulsation frequency is... The frequency is set close to the natural frequency of the sediment skeleton, typically between 50Hz and 100Hz, to generate a resonance effect. High-energy pulsed fluid is ejected from the jet nozzle 113, creating microcracks on the surface of the hard sediment and expanding them into fissures, forming a hydraulic wedging effect. The high-pressure jet impacts the humus layer on the surface of the riverbed sediment, which is 20-30cm thick, causing the compacted sediment to be fully suspended in the water, forming a mud-water mixture.

[0061] Online injection and mixing of low-viscosity agents: The central control unit 300 controls the three-way solenoid switching valve 131 to switch to the low-viscosity feed circuit 221. The low-viscosity remediation agent is drawn into the pipeline; this low-viscosity remediation agent is a bottom sediment remediation ecological filter media. The low-viscosity remediation agent has low-viscosity flow characteristics, with a dynamic viscosity of less than 5 mPa·s. The low-viscosity remediation agent is transported to the nozzle through the outer channel 112, where it is entrained by the high-pressure water jet from the inner channel 111. It is instantly mixed in the premixing chamber of the jet nozzle 113, forming a solidified liquid flow with high permeability, thus realizing the addition and solidification step. While impacting the bottom sediment, bottom sediment remediation ecological filter media is added to the mud-water mixture, promoting full contact between the filter media and fresh suspended pollutants.

[0062] Pressure-flow negative feedback regulation: To prevent pipeline overpressure rupture due to encountering localized, unbreakable obstacles under high-pressure conditions, the central control unit 300 implements pressure-flow negative feedback control. The central control unit 300 monitors the real-time fluid back pressure. The flow output of the high-pressure water pump set 210 is dynamically adjusted according to the following control law. : ;in: The adjusted pump flow rate; Maximum rated flow rate; Real-time fluid back pressure; The maximum safe pressure for the in-situ sediment solidification and remediation system is 10. It is usually set to 25MPa to 30MPa; To adjust the sensitivity coefficient, adjust the sensitivity coefficient. The value is typically set to 2-3. The pressure and flow negative feedback control strategy ensures that the real-time fluid back pressure is controlled. Approaching the upper limit of the safety pressure of the in-situ solidification and remediation system for sediment. At that time, pump flow rate The pressure drops rapidly, thus limiting further increases; while maintaining maximum rated flow rate when the real-time fluid back pressure is low. To ensure operational efficiency. For the variable frequency speed control of the high-pressure water pump set 210, those skilled in the art can use vector control or V / F control technology, which are well-known technologies in the field and will not be elaborated here.

[0063] When the central control unit 300 determines that the current medium is a soft medium, the sediment in-situ solidification and remediation system 10 automatically switches to the low-pressure micro-disturbance and thixotropic lock-in operation mode. The low-pressure micro-disturbance and thixotropic lock-in operation mode is designed for the thixotropic characteristics of high-water-content sludge, aiming to avoid backflow caused by high-pressure jets, while utilizing the thixotropic properties of the fluid to achieve in-situ solidification. The specific control strategy includes the following steps: Establishment of low-pressure constant-current transmission: To avoid excessive disturbance to the soft sediment, the central control unit 300 sends a flexible delivery command to the high-pressure water pump unit 210, switching the operating mode from pressure control to flow control. The pumping pressure of the high-pressure water pump unit 210 is significantly reduced to a low-pressure setpoint, typically set between 2 MPa and 5 MPa; simultaneously, a constant volumetric flow rate is maintained, typically set between 10 L / min and 30 L / min. At this point, the jet pressure no longer pulsates but remains stable, and the jet is injected into the sediment in a laminar flow manner. This low-pressure laminar flow injection method prevents the splashing and diffusion of sediment particles.

[0064] Switching to high-viscosity thixotropic agents: The central control unit 300 controls the three-way solenoid switching valve 131 to switch to the high-viscosity feed circuit 222. The high-viscosity repair agent begins to enter the delivery pipeline. The high-viscosity repair agent includes modified cement slurry or polymer gel. The high-viscosity repair agent exhibits shear-thinning properties, meaning its viscosity decreases when flowing at high speed in the pipeline, but rapidly recovers to a high viscosity when stationary.

[0065] Micro-disturbance stirring and in-situ lock-in: To facilitate the mixing of the high-viscosity remediation agent with the sediment without disrupting its overall structure, the central control unit 300 controls the coaxial dual-channel jet gun 110 to rotate at a low speed, typically set to 5 to 10 rpm. The rotation of the jet nozzle 113 generates a small shear field within a localized area, causing the thixotropic agent to temporarily liquefy under shearing and mix with the surrounding sludge. Once the mixed fluid leaves the shear zone (i.e., the jet stops or the gun is removed), the viscosity of the mixed fluid... Over time Gradually recovering, it forms a gel-like locked structure. The kinetic model of the viscosity recovery process is described as follows: ;in: The apparent viscosity of the mixed fluid as a function of time; The limiting viscosity of the fluid at an infinite shear rate; Let be the zero-shear viscosity of the fluid at rest, where The thixotropic recovery time constant is... The value is typically determined by the reagent formulation, with a typical range of 1 to 10 seconds. Utilizing the liquefaction, mixing, and solidification mechanisms of the medium's thixotropy, low-pressure micro-perturbation and thixotropic lockout operation modes prevent reagent loss, ensuring the in-situ remediation effect of soft sludge. For the measurement and characterization of fluid thixotropy, those skilled in the art can use a rotational rheometer, which is a standard experimental technique in this field.

[0066] During the switching process of the coaxial dual-channel jet gun 110 from mode A to mode B, or from mode B back to mode A, the fluid viscosity and the pressure of the in-situ solidification and repair system 10 for sediment will undergo a step change. To prevent water hammer effects in the pipeline that could damage the equipment and to ensure a smooth transition of the rheological modes, the central control unit 300 adopts a near-end switching transient response control strategy, the specific execution process of which includes the following steps: Pre-switch pressure offloading: When the central control unit 300 classifies according to media properties When the change generates a mode switching command, the central control unit 300 does not immediately activate the three-way solenoid switching valve 131. The central control unit 300 first performs a pressure unloading operation on the high-pressure water pump assembly 210. The central control unit 300 forcibly reduces the pressure setpoint of the high-pressure water pump assembly 210 to the safe switching pressure. Safe switching pressure The pressure is typically set between 1 MPa and 2 MPa. The pressure unloading operation releases the elastic energy in the pipeline bottom mud in-situ solidification and repair system 10, reducing the hydraulic resistance and seal wear when the valve core of the three-way solenoid switching valve 131 is activated.

[0067] Valve spool movement and dead time delay: Real-time fluid back pressure was monitored. Decrease to safe switching pressure Following this, the central control unit 300 sends a reversing pulse signal to the three-way solenoid switching valve 131. Considering the mechanical inertia of the three-way solenoid switching valve 131 from energization to the complete displacement of the valve core, the central control unit 300 sets a fixed dead-time delay. Dead zone delay time The default setting is typically 100ms to 300ms. (This refers to the dead time delay.) Inside, the high-pressure water pump set 210 is kept running at the lowest speed to ensure that the minimum lubrication flow is maintained in the pipeline and to prevent pump body cavitation caused by flow interruption.

[0068] Smooth Sigmoid Transition for Pressure Setting: After the three-way solenoid switching valve 131 completes the physical switch, the fluid medium changes. To avoid the pressure jump impacting the newly connected fluid circuit, the central control unit 300 uses a universal Sigmoid function to plan the pressure recovery trajectory. Target Pressure Setpoint Dynamic loading is performed according to the following smooth curve equation: ;in: The pressure setting value varies over time; The initial pressure for the pressure recovery process is typically set at the safe switching pressure. The target workload is the current operating mode. If switching to mode A, the target workload will be... If switched to Mode B, the target workload will be... The value is the low-pressure setting value. ; Transition slope coefficient, transition slope coefficient The transition slope coefficient is typically taken as 5 to 10. Used to control the rate of pressure rise; This is a time variable calculated from the moment the switchover is completed; For the transition center time, the transition center time The setpoint is typically between 0.5 and 1.0 seconds. The Sigmoid function controls the pressure setpoint. The pressure increases slowly in the initial stage, accelerates in the middle stage, and gradually approaches the target value. The nonlinear pressure loading method suppresses transient pressure overshoot caused by sudden changes in fluid momentum, ensuring the output stability of the coaxial dual-channel jet gun 110 under variable viscosity conditions. For PID controller parameter tuning, the central control unit 300 calls a pre-stored gain parameter table according to the characteristics of the currently connected fluid loop. Gain parameter table scheduling technology is a conventional control method in this field.

[0069] To ensure the remediation agent can be uniformly dispersed within the sediment and form a high-strength solidified body, the nozzle structure of the coaxial dual-channel jet gun 110 is designed based on the principle of jet entrainment. The coaxial dual-channel jet gun 110 utilizes the momentum transfer of high-speed fluid to achieve powerful stirring of the surrounding medium and induces rapid crystallization through microscale turbulent mixing. The specific physicochemical process includes the following steps: Formation of the jet negative pressure entrainment zone: When high-pressure or low-pressure fluid is ejected at high speed from jet nozzle 113, a strong shear layer is formed in the exit region of jet nozzle 113. According to Bernoulli's principle, the increase in flow velocity leads to a decrease in static pressure, thereby creating a local negative pressure zone around the jet core region. This local negative pressure zone entrains surrounding sediment particles into the main flow stream. The entrainment mixing efficiency is determined by the entrainment ratio. To measure, entrainment ratio Defined as the flow rate of entrained sediment. With nozzle outlet jet flow rate The ratio: ;in: The entrainment ratio; The volumetric flow rate of the sediment entrained into the jet; The jet volume flow rate at the nozzle outlet; The jet structure coefficient is the jet structure coefficient. Depending on the nozzle geometry, the value is typically 0.32; The density of the repair agent fluid; The density of the sediment medium; The distance along the jet axis; The outlet diameter of the jet nozzle 113.

[0070] The entrainment ratio formula shows that by optimizing the outlet diameter of the jet nozzle 113... and control the axial distance of the jet The coaxial dual-channel jet gun 110 can achieve quantitative entrainment of the surrounding bottom sediment, ensuring that the volume ratio of the repair agent to the bottom sediment is maintained within the design range.

[0071] Turbulent dissipation and micromixing: The entrained sediment particles undergo intense fragmentation and dispersion within the jet shear layer. Fluid kinetic energy is converted into turbulent pulsating kinetic energy, and ultimately into thermal energy through viscous dissipation. To ensure that remediation agent molecules can penetrate the interlayer structure of clay minerals, the mixing scale must reach the micrometer level. The mixing effect is determined by the Kolmogorov microscale. Decide: ;in: For turbulent micro-mixing scale; The kinematic viscosity of the mixed fluid; This refers to the turbulent energy dissipation rate. The high turbulent energy dissipation rate generated under high-pressure jet mode. This enables the micro-mixing scale of turbulent flow. The size is reduced, typically to the level of 10 to 50 micrometers. The fine turbulent vortices increase the contact surface area between the fluid and the solid particles, eliminating diffusion mass transfer resistance and providing homogeneous reaction precursors for subsequent chemical reactions.

[0072] Induced nucleation and crystallization kinetics: The uniformly mixed slurry follows different solidification mechanisms depending on the injected reagents under the current operating mode: When the in-situ solidification and remediation system 10 is in the penetration enhancement operating mode, the injected low-viscosity sediment remediation ecological filter media acts as an inducing agent for enhanced nitrogen and phosphorus removal. Utilizing its strong adsorption and ion conversion properties, the sediment remediation ecological filter media, whose main component is calcium silicate, releases Ca²⁺ into the water during mixing. Simultaneously, weak acid ions such as silicate ions enhance the alkalinity of the water. Under alkaline conditions, phosphorus in the water combines with Ca²⁺ to form CaHPO₄·2H₂O crystals, which adhere to the surface of the porous aggregate. This process utilizes the aggregate in the ecological filter media as seed crystals, reducing the interfacial free energy of crystal precipitation and achieving heterogeneous induced crystallization, thereby efficiently removing and fixing dissolved pollutants in the sediment pore water.

[0073] When the in-situ solidification and remediation system 10 is in viscous lock-in operation mode, the injected high-viscosity remediation agent mainly utilizes its hydration hardening properties or polymer network cross-linking properties. After micro-mixing, the remediation agent encapsulates soft sediment particles, forming a skeleton structure with a certain strength through thixotropic recovery and hydration reaction, thereby achieving the physical preservation and stabilization of convective plastic sediment.

[0074] The crystallization and solidification process follows the Avramy crystallization kinetics equation: ;in: For a moment Relative crystallinity, relative crystallinity This indicates the fraction of the total volume that has been cured. Let be the crystallization rate constant. Affected by temperature and reagent concentration, the typical value range is 0.1 to 0.5; Reaction time; The Avrami index. The Avramie index is related to the crystal growth mechanism and nucleation type. For the in-situ solidification process of sediment, it is related to the crystal growth mechanism and nucleation type. The value is usually between 2 and 3, representing a three-dimensional growth pattern.

[0075] The central control unit 300 directly affects the crystallization rate constant by regulating the injection rate of the repair agent and the jet stirring time. This allows for control over the setting time of the solidified material. Kinetic control ensures that the mixed slurry is in a plastic state before the coaxial dual-channel jet gun 110 is withdrawn from the borehole, and that it rapidly crystallizes and solidifies after withdrawal, forming a load-bearing pile structure.

[0076] Settlement remediation steps: After the disturbance, mixing, and chemical reaction are completed, the slurry mixed with the ecological filter media naturally settles back to the riverbed under gravity. After settling, the filter media continues to play a long-term pollutant reduction role in the bottom sediment and adsorbs pollutants from the overlying water body for further treatment, thereby restoring and enhancing the purification function of the bottom sediment.

[0077] The specific derivation and parameter determination of the Avramie equation can be obtained by those skilled in the art through differential scanning calorimetry or X-ray diffraction analysis, which are well-known techniques in the field of materials science.

[0078] To strictly prevent secondary diffusion of pollutants into surrounding water bodies due to excessive disturbance during sediment remediation operations, the central control unit 300 is equipped with a dynamic safety trigger mechanism based on environmental monitoring data. This dynamic safety trigger mechanism does not rely on a single concentration threshold but assesses environmental risk by calculating the flux characteristics of pollutant diffusion. Specific implementation steps include: Calibration and real-time monitoring of environmental background values: Before the coaxial dual-channel jet gun 110 is lowered to the operating depth, the sensor units in the turbidity flux monitoring array 410 collect initial turbidity data of the overlying water. The central control unit 300 continuously records the turbidity data within a set time window and calculates the arithmetic mean as the set environmental background turbidity value. .

[0079] The turbidity flux monitoring array 410 monitors the real-time turbidity value of the water column above the work point at a set sampling frequency. To quantify the diffusion rate of suspended particulate matter into the surrounding water, the central control unit 300 constructed a turbidity diffusion flux index. Turbidity diffusion flux index The calculation formula is: ;in: Turbidity diffusion flux index A comprehensive measure representing the intensity of suspended matter diffusion per unit time; For a moment The measured real-time turbidity value is in NTU. To set the ambient background turbidity value, the unit is NTU; The rate of change of turbidity over time is used to characterize the rapid growth trend of a pollution plume. Concentration weighting coefficient (dimensionless), concentration weighting coefficient The value is typically between 0.6 and 0.8. Rate weighting coefficient (with time dimension, unit is seconds), rate weighting coefficient The value is typically taken as 0.2 to 0.4, used to balance dimensions and assess the growth trend of pollution plumes. The above formula is an engineering empirical model. and The specific values ​​are obtained based on on-site hydrological environmental calibration. The turbidity diffusion flux index calculation model takes into account both the absolute pollution level and the pollution growth rate. Compared to a single threshold determination, the turbidity diffusion flux index... It can identify the risk of sudden sediment outbursts earlier.

[0080] Determination of multi-level circuit breaker threshold: The central control unit 300 has two preset safety circuit breaker thresholds: a warning threshold and a control unit 300. and circuit breaker threshold When the turbidity diffusion flux index satisfy < < The central control unit 300 determines that the in-situ sediment solidification and remediation system 10 is under slight disturbance. At this time, the central control unit 300 does not interrupt the operation, but automatically triggers a frequency reduction and pressure reduction strategy. The central control unit 300 reduces the pumping pressure of the high-pressure water pump set 210 to 80% of the current set value and reduces the rotational speed of the coaxial dual-channel jet gun 110 to 50% of the current speed to slow down the lifting speed of sediment particles. When the turbidity diffusion flux index... satisfy > At that time, the central control unit 300 determined that the in-situ sediment solidification and remediation system 10 was in a state of severe diffusion risk and immediately triggered the hard fuse protection procedure. Fuse threshold. The setting is usually based on environmental assessment standards, and is typically set as background turbidity. The flux value is 3 to 5 times that of the previous value.

[0081] Negative pressure reverse suction and environmental reset: Once the hard-blowout protection procedure is triggered, the central control unit 300 immediately stops the operation of the high-pressure water pump set 210 and the in-situ solidification and remediation system 10 for the feed sediment, and simultaneously starts the vacuum negative pressure pump station 230. The vacuum negative pressure pump station 230 generates suction through the inner channel 111 of the coaxial dual-channel jet gun 110, forming an inward negative pressure flow field near the central hole of the jet nozzle 113. The negative pressure reverse suction operation aims to prevent contaminants in the borehole from continuing to migrate to the surrounding water body by establishing a reverse pressure gradient, and to pump locally high-concentration turbid liquid into the waste liquid treatment tank. Reverse suction duration. The duration of reverse absorption is positively correlated with the magnitude of the excess flux. The control function is: ;in: The duration of negative pressure reverse suction; The basic reverse absorption time is usually set to 10 to 30 seconds; The instantaneous turbidity diffusion flux index at the time of triggering the circuit breaker; The circuit breaker threshold; is the base of the natural logarithm.

[0082] By performing a negative pressure reverse suction operation, the coaxial dual-channel jet gun 110 can actively eliminate localized turbidity caused by operational errors. (Real-time turbidity value to be displayed.) Falling back to the warning threshold The following and maintain a stable time Subsequently, the central control unit 300 automatically releases the fuse, allowing the in-situ sediment solidification and repair system 10 to reset and resume operation. Regarding the calibration method for the turbidity sensor, those skilled in the art can use formalin standard solution for calibration, which is a well-known technique in the field.

[0083] To further verify the practical application effect of the in-situ solidification and remediation system 10 and its control method for sediment described in this invention, the following field application examples were carried out in conjunction with the above control logic and operation mode.

[0084] Example 1: Eutrophication Treatment of Urban Landscape Rivers This embodiment selects a city landscape river as the treatment target. The river is approximately 1 kilometer long with an average depth of 1.5 meters. The bottom sediment is compacted, and the overlying water is severely eutrophic. During the operation, the central control unit 300 first controls the coaxial dual-channel jet gun 110 to make exploratory contact. When the in-situ sediment solidification and remediation system 10 determines that the current medium is hard sediment, the system automatically switches to the permeability enhancement state. During the process, granular sediment remediation ecological filter media containing modified zeolite and calcium-based materials is injected into the disturbed area. (Refer to Appendix) Figure 3 To verify the pollutant reduction capacity of the injected ecological filter media, continuous monitoring of the treated area was conducted for 45 days, divided into three 15-day cycles. Monitoring data showed that: Total nitrogen removal effect: as shown in the attached figure Figure 3 As shown in the upper curve, the TN removal rate reached 83.1%-88.24% at the end of the first cycle. As the filter media established a stable ion exchange and bio-attachment environment in the sediment, the TN removal rate stabilized at over 93.4% in the second and third cycles, reaching a maximum of 95.55%.

[0085] Total phosphorus removal effect: as shown in the attached document Figure 3 As shown in the lower curve, the TP removal rate exhibited a rapid upward trend, reaching 88.8%-90.7% in the first cycle and maintaining a high-efficiency removal level of over 90% in subsequent cycles. A comprehensive on-site assessment one week later showed a decrease in ammonia nitrogen and total phosphorus content in the sediment, and an improvement in the transparency of the overlying water, validating the effectiveness and safety of the high-pressure infiltration operation.

[0086] Example 2: Remediation of Localized Heavy Metal Pollution Areas in a Small Lake This embodiment addresses a localized contaminated area of ​​approximately 500 square meters at the entrance of a lake. The sediment in this area is soft, deep, and contains excessive levels of heavy metals. During the operation, the in-situ sediment solidification and remediation system 10 automatically switches to a viscous lock-in state when the medium is identified as soft sediment. A coaxial dual-channel jet gun 110 rotates and stirs the sediment at a low speed within a depth of 30 cm. Utilizing the thixotropic recovery principle, the mixed agent rapidly recovers its high viscosity after agitation ceases, effectively fixing the heavy metals in situ within the gel framework and suppressing the release of odorous gases from the sediment. Post-construction monitoring shows that the shear strength of the sediment is enhanced, and the leaching toxicity of heavy metals is below the relevant standard limits, achieving precise and targeted remediation of soft, contaminated sediment.

Claims

1. A method for in-situ solidification and remediation of river and lake bottom sediment, characterized in that, Includes the following steps: The coaxial dual-channel jet gun (110) is placed in the working position, and the mechanical vibration signal and pipeline fluid back pressure signal of the coaxial dual-channel jet gun (110) are collected synchronously using the sensing components. The mechanical vibration signal and the pipeline fluid back pressure signal are processed by the central control unit (300), and the equivalent acoustic impedance index and normalized flow resistance deviation of the contact medium are calculated respectively. The contact medium is mapped to either a hard medium category or a soft medium category based on the equivalent acoustic impedance index and the normalized flow resistance deviation. When the sediment is identified as a hard medium, the in-situ solidification and repair system (10) operates in the penetration enhancement mode, outputs a high-pressure jet and injects low-viscosity repair material. When the sediment is identified as a soft medium, the in-situ solidification and repair system (10) operates in a viscous lockout mode, outputting low-pressure fluid and injecting high-viscosity repair material. During the execution of the corresponding operation mode, the turbidity diffusion flux index of the operation area is monitored synchronously, and when the turbidity diffusion flux index triggers the circuit breaker condition, the current operation mode is interrupted and a negative pressure reverse suction operation is performed.

2. The in-situ solidification and remediation method for river and lake bottom sediments according to claim 1, characterized in that, The sensing component includes: A piezoelectric vibration sensor (121) rigidly coupled to the outer wall of the coaxial dual-channel jet gun (110) is used to collect the mechanical vibration signal; And a precision pressure transmitter (211) installed on the feed pipeline of the in-situ solidification and repair system (10) for collecting the back pressure signal of the pipeline fluid.

3. The in-situ solidification and remediation method for river and lake bottom sediments according to claim 1, characterized in that, The step of using the central control unit (300) to process the mechanical vibration signal and calculate the equivalent acoustic impedance index includes: The power spectral density function is obtained by performing a frequency domain transformation on the mechanical vibration signal; The power spectral density function is integrated over a set frequency band using a frequency weighting function to obtain the equivalent acoustic impedance index. The frequency weighting function is configured as a linearly increasing function or an exponentially increasing function that increases the weight as the frequency increases, in order to highlight the high-frequency reverberation characteristics of the hard layer.

4. The in-situ solidification and remediation method for river and lake bottom sediments according to claim 1, characterized in that, The step of using the central control unit (300) to process the pipeline fluid back pressure signal and calculate the normalized flow resistance deviation includes: The steady-state pressure value is obtained by performing sliding window averaging on the pipeline fluid back pressure signal; The normalized flow resistance deviation is obtained by calculating the incremental ratio of the steady-state pressure value relative to the stored pure water back pressure reference value. Monitor the rate of change of the normalized flow resistance deviation within adjacent control cycles, and maintain the numerical output of the previous moment when the rate of change exceeds a set rate of change threshold.

5. The in-situ solidification and remediation method for river and lake bottom sediments according to claim 1, characterized in that, The step of mapping the contact medium to a hard medium category or a soft medium category based on the equivalent acoustic impedance index and the normalized flow resistance deviation includes: Construct a two-dimensional feature space with the normalized flow resistance deviation and the equivalent acoustic impedance index as coordinate axes; The decision region is divided in the two-dimensional feature space using acoustic impedance threshold and flow resistance deviation threshold. When the equivalent acoustic impedance index is greater than the acoustic impedance threshold, it is determined to be the hard medium category; When the equivalent acoustic impedance index is not greater than the acoustic impedance threshold and the normalized flow resistance deviation is greater than the flow resistance deviation threshold, it is determined to be the soft medium category.

6. The in-situ solidification and remediation method for river and lake bottom sediments according to claim 1, characterized in that, The in-situ solidification and remediation system (10) for sediments operates in the enhanced penetration mode, and the steps of outputting high-pressure jets and injecting low-viscosity remediation materials include: The high-pressure water pump set (210) is controlled to output the high-pressure jet with a set frequency pulsation, and the hydraulic wedge effect is used to break the bottom mud platen layer. The control fluid switching valve assembly (130) switches the passage to introduce the low-viscosity repair material, which exhibits Newtonian fluid properties, into the outer channel (112) of the coaxial dual-channel jet gun (110). The low-viscosity repair material is drawn into and injected into the mud fissures by the suction negative pressure generated at the jet nozzle (113) by the high-pressure jet.

7. The in-situ solidification and remediation method for river and lake bottom sediments according to claim 1, characterized in that, The in-situ solidification and remediation system (10) for sediments operates in the viscous lockout mode, and the steps of outputting low-pressure fluid and injecting high-viscosity remediation material include: The high-pressure water pump unit (210) is controlled to reduce its output power and maintain a constant flow rate, outputting the low-pressure fluid in a laminar state; The control fluid switching valve assembly (130) switches the passage to introduce the high-viscosity repair material, which exhibits non-Newtonian fluid properties, into the outer channel (112) of the coaxial dual-channel jet gun (110). The coaxial dual-channel jet gun (110) generates a shear force field by rotating at low speed, causing the high-viscosity repair material to undergo thixotropic liquefaction and mix with the bottom mud. After leaving the shear force field, the viscosity is restored to form a coating structure.

8. The in-situ solidification and remediation method for river and lake bottom sediments according to claim 1, characterized in that, The step of synchronously monitoring the turbidity diffusion flux index of the work area includes calculating the turbidity diffusion flux index in the following manner: The difference between the real-time turbidity value and the set environmental background turbidity value is obtained by using a turbidity flux monitoring array (410), and the absolute pollution component is obtained by weighting the difference. The rate of change of the real-time turbidity value over time is obtained, and the pollution growth component is obtained by weighted calculation of the rate of change. The turbidity diffusion flux index is obtained by summing the absolute pollution component and the pollution growth component.

9. A method for in-situ solidification and remediation of river and lake bottom sediments according to claim 6, characterized in that, When the turbidity diffusion flux index triggers the circuit breaker condition, the steps of interrupting the current operating mode and performing negative pressure reverse suction operation include: Cut off the supply path of the high-pressure water pump unit (210) and the repair materials; Isolate the high-pressure water pump set (210) and connect it to the vacuum negative pressure pump station (230). The vacuum negative pressure pump station (230) uses the inner channel (111) of the coaxial dual-channel jet gun (110) to construct a suction field and recover the suspended matter in the area of ​​the jet nozzle (113); The duration of reverse absorption is determined based on the turbidity diffusion flux index at the time of triggering the circuit breaker.

10. An in-situ solidification and remediation system for river and lake bottom sediments, characterized in that, A method for in-situ solidification and remediation of river and lake bottom sediments as described in any one of claims 1 to 9, comprising: The underwater operation unit (100) has a coaxial dual-channel jet gun (110) for outputting fluid and repair materials, and the coaxial dual-channel jet gun (110) is equipped with a sensing component and a fluid switching valve assembly (130). The water-based material supply unit (200) includes a high-pressure water pump group (210) for providing power, a dual-path rheological material supply group (220) for providing repair materials of different viscosities, and a vacuum negative pressure pump station (230) for providing suction. The peripheral monitoring unit (400) has a turbidity flux monitoring array (410) arranged around the perimeter of the work area. The central control unit (300) is communicatively connected to the underwater operation unit (100), the surface feeding unit (200) and the peripheral monitoring unit (400). The central control unit (300) is used to adjust the operation mode and perform fuse protection based on the feedback of the sensing components.

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